/*
 *  Licensed to the Apache Software Foundation (ASF) under one or more
 *  contributor license agreements.  See the NOTICE file distributed with
 *  this work for additional information regarding copyright ownership.
 *  The ASF licenses this file to You under the Apache License, Version 2.0
 *  (the "License"); you may not use this file except in compliance with
 *  the License.  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 *  Unless required by applicable law or agreed to in writing, software
 *  distributed under the License is distributed on an "AS IS" BASIS,
 *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *  See the License for the specific language governing permissions and
 *  limitations under the License.
 */
package com.googlecode.httl.support.util;

import java.io.Serializable;
import java.util.Iterator;
import java.util.LinkedList;
import java.util.Collections;
import java.util.List;

/**
 * LinkedStack. (Tool, Prototype, ThreadUnsafe)
 * 
 * @author Liang Fei (liangfei0201 AT gmail DOT com)
 */
public class LinkedStack<T> implements Serializable {

	private static final long serialVersionUID = 1L;

	private final LinkedList<T> stack = new LinkedList<T>();

	public int size() {
		return stack.size();
	}

	public boolean isEmpty() {
		return stack.size() == 0;
	}

	public void push(T value) {
		stack.addLast(value);
	}

	public T pop() {
		T value = peek();
		stack.removeLast();
		return value;
	}

	public T peek() {
		if (isEmpty()) {
		    return null;
		}
 		return stack.getLast();
	}

	public void poke(T value) {
		if (! isEmpty()) {
		    stack.removeLast();
		}
		push(value);
	}

	public void clear() {
		stack.clear();
	}

	public Iterator<T> iterator() {
		return Collections.unmodifiableList(stack).iterator();
	}

	public List<T> toList() {
		return Collections.unmodifiableList(stack);
	}

	public String toString() {
		return stack.toString();
	}

    @Override
    public int hashCode() {
        final int prime = 31;
        int result = 1;
        result = prime * result + ((stack == null) ? 0 : stack.hashCode());
        return result;
    }

    @Override
    public boolean equals(Object obj) {
        if (this == obj) return true;
        if (obj == null) return false;
        if (getClass() != obj.getClass()) return false;
        LinkedStack<?> other = (LinkedStack<?>) obj;
        if (stack == null) {
            if (other.stack != null) return false;
        } else if (!stack.equals(other.stack)) return false;
        return true;
    }

}
